Spectrum Allocation for Base Station

ABSTRACT

Embodiments include processes, systems, and devices that allow a white space base station to request available frequency ranges for white space transmission in a local area. A white space finder service models a primary user device&#39;s transmission signal propagation area using terrain data associated with the local area of the primary user device. The white space finder service also determines, based on the location of the white space base station and the modeled propagation area, one or more locally available, non-interfering frequency ranges and provides them to the white space base station. The white space base station compares the provided frequency ranges to policies and selects one or more of the available frequencies that accommodate the policies. The white space base station also maps the transmission frequency ranges to virtual frequency ranges for transmission by a software-defined radio employing spectrum virtualization.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 35 U.S.C. 371 National Stage Application ofInternational Application No. PCT/CN2011/073647, filed May 4, 2011, theentire contents of which are incorporated herein by reference.

BACKGROUND

White space frequency bands are frequency bands allocated to television(TV) broadcasting service and to wireless microphone service, but notused in a local geographic area. Recent Federal Communication Commission(FCC) rules allow unlicensed access to white space frequency bands inthe United States as long as such access does not interfere with TV andwireless microphone transmission (i.e., “incumbent” or “primary user”access to the frequency bands). Non-U.S. jurisdictions may also in thefuture implement similar provisions for access to television frequencybands. Available white space frequency bands may have variablebandwidths, and they may be non-contiguous and location-specific. Theseaspects make white space transmission networks different fromconventional wireless transmission networks. Conventional wirelesssolutions utilize hardware chips for data transmission. Such hardwarechips are limited to certain physical layer and media access controlprotocols, as well as certain transmission frequency bands. Hard-codedprotocols cannot utilize non-contiguous frequency bands. Furthermore,supporting both long and short-distance white space transmissionrequires either multi-protocol chips or multiple hard-coded chips.

BRIEF SUMMARY

This Summary is provided in order to introduce simplified concepts ofresource download policy generation, which are further described belowin the Detailed Description. This summary is not intended to identifyessential features of the claimed subject matter, nor is it intended foruse in determining the scope of the claimed subject matter.

In embodiments, a spectrum manager of a white space base stationrequests and receives one or more available frequency bands fortransmission in the local area of the white space base station. Thespectrum manager compares the available frequency bands to one or morepolicies, such as regulatory policies or technical requirements, andselects some or all of the available frequency bands that match thepolicies. The spectrum manager also maps the available frequency bandsto one or more virtual frequency bands, such as for use by asoftware-defined radio employing spectrum virtualization. A spectrumvirtualization module of the white space base station maps a virtualbaseband presented to a physical layer of a wireless protocol to aphysical baseband associated with the selected physical frequency bands.Data modulated by the physical layer of the wireless protocol accordingto a virtual frequency band is transmitted on the selected physicalfrequency band.

A white space finder service receives requests for available frequencybands and utilizes terrain data to model an area over whichtransmissions of one or more primary user transmission devices arelikely to propagate. Based on the modeled propagation areas as well aslocations and channels employed by primary user transmission devices,the white space finder service selects one or more frequency bands thatare non-interfering with primary users and available in the local areaof the white space base station.

BRIEF DESCRIPTION OF THE DRAWINGS

The Detailed Description is set forth with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Theuse of the same reference numbers in different figures indicates similaror identical items.

FIG. 1 is a schematic diagram of an example environment usable toallocate white space spectrum for transmission by a white space basestation.

FIG. 2 is a block diagram of an example white space base station.

FIG. 3 is a block diagram of an example white space finder service.

FIG. 4 is a flow diagram showing an example process of frequencyselection by a white space base station.

FIG. 5 is a flow diagram showing an example process for determination oflocation-specific, non-interfering white space frequency by awhite-space finder service.

FIG. 6 illustrates a local geographic area of a white space basestation, and a modeled propagated area of its transmission signal.

FIG. 7 illustrates a transmission environment including a base stationand wireless clients configured to use spectrum virtualization.

FIG. 8 illustrates an interworking between a radio frequency front-end,the spectrum virtualization layer, and a physical layer duringtransmission between a sender and a receiver.

FIG. 9 illustrates a block diagram of a spectrum virtualization layerarchitecture.

FIG. 10 illustrates a spectrum virtualization layer configured to mapdifferent wireless transmission protocols to different radio front-ends.

FIG. 11 is a flow diagram showing an example process for interface callsto a spectrum virtualization layer.

FIG. 12 is a flow diagram showing an example process for timingvirtualization.

DETAILED DESCRIPTION Overview

As discussed above, the availability of white space frequency bands islocation-specific. The present disclosure therefore includes processes,systems, and devices for allocating white space frequency bands forwhite space base stations based at least on the location of the whitespace base station, regulatory policies, and/or transmissionrequirements of the white space base station. Also, as mentioned above,white space frequency ranges may be non-contiguous and variable. Thus,embodiments utilize a software-defined radio for more flexible whitespace transmissions. Some embodiments may utilize Microsoft® ResearchSoftware Radio (SORA) platform to implement the software-defined radio.

In one aspect of the present disclosure, a white space finder serviceprovides data to white space base stations regarding available whitespace frequency bands that may be utilized without causing interferencewith primary users (such as television transmitters or licensed wirelessmicrophones). The white space finder service may be a web-based serviceable to provide location-specific information about spectrumavailability to white space base stations. Information regarding thelocations of primary user transmitters that are near the white spacebase station is combined with terrain data to determine a geographicarea that wireless transmissions of one or more primary usertransmitters are likely to propagate. Based on the determined geographicpropagation areas, as well as the location of the white space basestation, the white space finder service determines available white spacefrequency bands for use by the white space base station. The propagationarea and interference determinations may be modeled, in variousembodiments, using one of various propagation models such as theLongley-Rice radio signal propagation model. The white space finderservice selects white space frequency ranges that are not likely tointerfere with primary users.

Without utilizing terrain data and propagation models to determine thesignal propagation area of the primary users, a relatively conservativeestimate of the propagation area would have to be made in order to bereasonably certain that white space base station transmissions do notinterfere with primary users. Using propagation modeling may increasethe sizes of the geographical areas within which white space devices areable to utilize white space frequency bands without sacrificing thenon-interference requirement of white space frequency transmission. Thismay increase the availability of white space frequency transmissionsgenerally.

In another aspect of the present disclosure, a spectrum manager of awhite space base station determines one or more physical transmissionfrequency bands of white space spectrum to use for transmissions. Thespectrum manager receives information about one or more locallyavailable, non-interfering white space frequency transmission bands froma white space finder service. The spectrum manager determines which ofthe one or more physical transmission frequency bands are to be used fortransmission based on regulatory policies, technical requirements of thetransmission, and characteristics of the available transmission bands.

Regulatory policies include FCC or other regulatory agency regulations.Non-limiting examples of regulatory policies include time of day,duration of availability, guard band requirements, transmission powerlevel limits, and other types of policies. Technical requirements fortransmission may be specific to a wireless transmission protocol that isutilized for the transmission. Non-limiting examples of technicalrequirements include bandwidth requirements, transmission powerrequirements, duplex transmission, simplex transmission, and so forth.The spectrum manager may compare the available physical frequency bandsto the technical requirements and select one or more of the availablephysical frequency bands that allow the transmissions to comply with thepolicy requirements.

In another aspect of the present disclosure, the spectrum manager mapsone or more physical transmission bands (selected for white spacetransmission) to one or more “virtual” transmission bands that areutilized by a wireless transmission protocol of the white space basestation. For example, the white space base station may employconventional wireless transmission protocols (such as Wi-Fi®, protocolswithin the 802.11 suite of protocols, code division multiple access(CDMA) based protocols, carrier sense multiple access (CSMA) basedprotocols, time division multiple access (TDMA) based protocols, andothers), or combinations thereof. Such conventional wirelesstransmission protocols may not support variable or non-contiguousfrequency transmissions, and such conventional wireless transmissionprotocols may have requirements for transmissions on specific frequencybands that differ from the selected white space frequency bands. Someembodiments may therefore utilize a communications module to generatemodulated baseband signals on “virtual” frequency bands (i.e., virtualbaseband signals) that correspond to the frequency bands according tothe conventional wireless transmission protocols. Various embodimentsmay also utilize a spectrum virtualization layer, as is describedelsewhere within this Detailed Description, to shape the virtualbaseband signals into physical baseband signals for radio transmissionaccording to the selected physical frequency bands in the white spacespectrum. The spectrum manager, upon selection of the available physicaltransmission frequency bands, maps the physical transmission frequencybands to the virtual frequency bands. The spectrum virtualization layerenforces the mapping.

To support the mapping of a virtual frequency band to a physicaltransmission band that is a different size, the spectrum virtualizationlayer uses a virtual clock so that the wireless protocol can be used totransmit at a slower or faster rate than is associated with the fixedfrequency band specified by the wireless protocol. To support mapping ofa virtual frequency band to an equal-sized physical spectrum band, avirtual clock is used in some but not all embodiments. To support themapping of a virtual frequency band to non-contiguous physicaltransmission bands, the spectrum virtualization layer employs splittersto split up signals for transmission, and mixers to combine receivedsignals during reception.

Embodiments also include wireless clients configured to communicate witha wireless base station, such as a white space base station. Wirelessclients may also include a spectrum virtualization layer that behaves ina same or similar way as the spectrum virtualization layer in a basestation. A spectrum manager of a wireless client may be configured tomap virtual transmission frequency bands to one or more physicaltransmission frequency bands, and the spectrum virtualization layer ofthe wireless client may be configured to enforce this mapping.

Although various embodiments may be described herein as being related to“white space” transmissions, “white space” networks, “white space” basestations, and “white space” clients, embodiments of the presentdisclosure are not limited to white space environments. Rather,embodiments include transmissions, networks, base stations,environments, and clients that are usable and/or compatible with any ofvarious Dynamic Spectrum Access (DSA) networks. Embodiments refer to“white space” networking for the sake of discussion, and such referencesshould not be taken in a limiting way.

The processes, systems, and devices described herein may be implementedin a number of ways. Example implementations are provided below withreference to the following figures.

Example Environment for Frequency Allocation

FIG. 1 is a schematic diagram of an example environment 100 usable toallocate spectrum, such as white space spectrum, for transmission by abase station, such as a white space base station. Environment 100 mayinclude white space base station 102 and white space finder service 104.White space base station 102 may be implemented on various suitablecomputing device types that are capable of implementing a white spacebase station. Suitable computing device or devices may include, or bepart of, one or more personal computers, servers, server farms,datacenters, combinations of these, or any other computing device(s)capable of storing and executing all or part of a white space basestation service.

In addition, white space finder service 104 may also be implemented onvarious suitable computing device types that are capable of implementinga white space finder service. Suitable computing device or devices mayinclude, or be part of, one or more personal computers, servers, serverfarms, datacenters, combinations of these, or any other computingdevice(s) capable of storing and executing all or part of a white spacefinder service.

Communication network 106 may include one or more of the Internet, widearea networks, local area networks, personal area networks, acombination of these, and others, any or all of which may be wiredand/or wireless. White space base station 102 and white space finderservice 104 may be coupled to communication network 106 using variouscommunication connections and protocols.

In the illustrative example of FIG. 1, white space base station 102includes user mode software services 108, kernel software services 110,and radio hardware 112. User mode software services 108 include aspectrum manager 114 having an availability module 116. The availabilitymodule 116 is configured to request and receive data regarding locallyavailable, non-interfering white space frequency bands from white spacefinder service 104 or radio hardware 112. The spectrum manager 114includes policy module 118 which has one or more policies, such asregulatory policies and technical requirements for wireless transmissionby the white space base station. Some or all of such policies may or maynot be received from white space finder service 104, or another service.Non-limiting examples of regulatory policies include guard bandsrequirements, power mask requirements, times that white space frequencybands are available, acceptable transmission power level ranges, and soforth. The technical requirements may include requirements specified byone or more wireless protocols employed by the white space base station102. Non-limiting examples of such wireless protocol specificationrequirements include single or multicarrier modulation requirements,power transmission level requirements, duplex/simplex transmissionrequirements, variable upload/download transmission requirements, and soforth.

Decision module 120—also in spectrum manager 114—is configured tocompare the one or more available physical transmission frequency bandsreceived by availability module 116 to the policies of policy module118, and to select ones of the one or more physical transmissionfrequency bands suitable for transmission according to the policies. Inone non-limiting example, policy module 118 may include a technicalrequirement for 1 megahertz bandwidth and a regulatory policyrequirement to include a 100 kilohertz guard band. Decision module 120may select one or more of the available physical transmission frequencybands to meet those policy requirements. Decision module 120 may selecttwo or more non-contiguous available physical transmission frequencybands to meet the policy requirements.

User mode software services 108 may include base station service 122configured to provide a general base station service to wireless clientssuch as a geo-location service and web caching, access connectionmanager 124 configured to control user access rights and connectivity,and security manager 126 configured to provide security services ofwhite space base station 102 such as access control lists,authentication, wireless encryption, and so forth.

Kernel software services 110 includes communication module 128,configured to provide a software radio service. Communication module 128includes spectrum virtualization module 130 configured to providespectrum virtualization services to one or more wireless transmissionprotocols 132-M. Wireless transmission protocols 132-M may include mediaaccess control (MAC_(M)) layers and physical layers (PHY_(M)) for usewith wireless transmission protocols 132-M.

Radio hardware 112 may be implemented as a white-space radio front-endboard, or other radio hardware. Such hardware may be for example a WBXfrom Ettus Research LLC. Radio hardware 112 may include one or moreradio transceivers 134-N and sensing hardware 136. One or more radiotransceivers 134-N may include radio-front ends which may include analogradio transmission and reception circuitry, antenna(s),analog-to-digital converter (ADC) circuitry, and digital-to-analogconverter (DAC) circuitry. Sensing hardware 136 may be configured toprobe and/or sense the availability of one or more physical transmissionfrequency bands according to embodiments. In some embodiments,availability module 116 is configured to query sensing hardware 136 foravailable frequency bands. Sensing hardware 136 may be a radiotransceiver similar to one or more radio transceivers 134-N. Inalternate embodiments, a single radio transceiver is configured to actas both a transceiver and a sensing hardware. Various aspects of radiohardware 112 may be reconfigurable to transmit on various frequencies,such as frequencies that cover TV spectrum bands.

Spectrum virtualization module 130 is configured to perform digitalmodulation. In conventional wireless transmission, digital modulationmaps a binary sequence (i.e., a bit stream) to a segment of digitalwaveform samples, called symbols. At a receiver, the symbols aredemodulated to retrieve the embedded binary information. Basebandsignals are not suitable to transmit directly; thus an RF front-end isconfigured to convert the digital baseband samples into high-frequencyanalog radio signals for transmission. The receiving RF front-endselects the desired radio frequency signals, down-converts the signals,and digitizes them to digital baseband signals.

With reference to the Open Systems Interconnection model (OSI model),PHY layers are analogous to layer 1 protocols and MAC layers areanalogous to layer 2 protocols. The spectrum virtualization module canbe thought of as implementing a spectrum virtualization layer at layer“0.5” of the OSI model.

One or more wireless transmission protocols 132-M may be conventionalprotocols. As noted above, conventional wireless transmission protocolsmay be incompatible with white space frequency bands and may beincompatible with variable or non-contiguous frequency bands. The PHYlayers of one or more wireless transmission protocols 132-M modulatebaseband signals for transmission on a fixed wireless frequency band,which may be different from the selected white space frequency bands.Spectrum virtualization module 130 treats these fixed wireless frequencybands as “virtual” frequency bands, and the baseband signals modulatedby the PHY layers as “virtual” baseband signals, since white space basestation 102 does not actually transmit on the fixed wireless frequenciesof the PHY layers. Spectrum virtualization module 130 instead reshapesthe virtual baseband signals that have been modulated according to thevirtual frequency bands into physical baseband signals for transmissionover the physical white space transmission bands.

Spectrum virtualization module 130 can be thought of as presenting a“virtual baseband” to one or more wireless transmission protocols 132-M.During transmission, spectrum virtualization module 130 intercepts thevirtual baseband signals and performs real-time reshaping of the virtualbaseband signals so that the virtual baseband of the PHY layers maps tothe physical transmission frequency bands. During reception, spectrumvirtualization module 130 intercepts the received physical basebandsignals and performs inverse reshaping to create virtual basebandsignals for passing to the PHY layers. In various embodiments, spectrumvirtualization module 130 enforces the spectrum mapping provided byspectrum manager 114 and allows white space base station 102 to utilizeconventional PHY designs without modifications to the PHY standards.

As noted above, availability module 116 may request a list of availablephysical transmission frequency bands. This request may be sent to whitespace finder service 104 via communication network 106. White spacefinder service 104 includes reception module 138 configured to receivethe request. The request may be accompanied by a location of white spacebase station 102. Propagation module 140, in white space finder service104, is configured to determine, based on a location of a primaryspectrum user (such as a television signal transmitter or a licensedwireless microphone user) that is near white space base station 102 andterrain data of a physical area near that location, a geographic areaover which transmissions from the primary spectrum user are likely topropagate. Interference determination module 142 is configured todetermine, based on the propagation area and the location of white spacebase station 102, whether transmissions of white space base station 102will potentially interfere with transmissions of the one or more primaryuser devices. Based on the results of the interference determination,send module 144 is configured to send one or more locally available,non-interfering physical transmission frequency bands to white spacebase station 102 that are available for white space base station 102 touse. Alternatively, send module 144 may provide data indicative ofphysical transmission frequency bands that are not available for use bywhite space base station 102. Send module 144 may also send one or morepolicies, such as regulatory policies, for use by decision module 120 inselecting frequency bands for transmission. Send module 144 may alsosend additional information, such as recommendations for which spectrumband is most beneficially used at the base station.

Some embodiments may allow primary users to volunteer their spectrum foruse in white space transmissions. Such primary users can add theirspectrum to the white space finder database. Revocation module 146 isconfigured to receive, from a primary user, a revocation of avoluntarily provided spectrum and to send the revocation to white spacebase station 102. Upon receiving a revocation of a frequency band thatis in use, decision module 120 is configured to select new ones of thephysical frequency bands for transmission.

Propagation module 140 and interference determination module 142together determine one or more physical transmission frequency bandsusable by white space base station 102 for non-interferingtransmissions. The propagation area and interference determinations maybe modeled, in embodiments, using one of various propagation models suchas the Longley-Rice radio signal propagation model. Geographic areainset 148 shows a location of white space base station 102 (marked “BS”in geographic area inset 148) along with the locations of primary usertransmission devices (denoted “TR” in FIG. 1) and various physicalfeatures such as hills, buildings, and a lake. The shaded area 150 showsan area over which transmissions from TR 152 are likely to propagate.Interference determination module 142 is configured to determine whatfrequencies that white space base station 102 may transmit on to avoidinterfering with the primary users TR. In the illustrative example shownin geographic area inset 148, white space base station 102 is within thepropagation area 150, but outside of another transmission propagationarea associated with TR 154. Thus, interference determination module 142may determine that white space base station 102 is allowed to transmitusing a frequency utilized by TR 154, but not using a frequency utilizedby TR 152. This potentially prevents white space base station 102 frominterfering with transmissions by TR 152—even though white space basestation 102 is within the modeled propagation area 150—because TR 152and white space base station 102 would utilize different frequencies.This also potentially prevents white space base station 102 frominterfering with TR 154—even though white space base station 102 usesthe same frequency band as TR 154—because white space base station 102is outside of the modeled propagation area associated with TR 154.Propagation module 140 may determine propagation area 150 based onterrain data, such as the existence of the lake and the hill. Forexample, the hill may shield transmissions from TR 152 and thereforedecrease the size of propagation area 150, for example.

Example White Space Base Station

FIG. 2 is a block diagram of an example white space base station 200.White space base station 200 may be configured as any suitable computingdevice capable of implementing base station services. According tovarious non-limiting examples, suitable computing devices may includepersonal computers (PCs), servers, server farms, datacenters,combinations of these, or any other computing device(s) capable ofstoring and executing all or part of a white space base station service.

In one example configuration, white space base station 200 comprises oneor more processors 202 and memory 204. White space base station 200 mayalso contain communication connection(s) 206 that allow communicationswith various devices such as for example white space finder service 104,such as is described in FIG. 1. The white space base station 200 mayalso include one or more input devices 208, such as a keyboard, mouse,pen, voice input device, touch input device, etc., and one or moreoutput devices 210, such as a display, speakers, printer, etc. coupledcommunicatively to the processor(s) 202 and memory 204.

White space base station 200 includes radio hardware 212. Radio hardware212 may be implemented as a white-space radio front-end board, or otherradio hardware. Radio hardware 212 includes one or more radiotransceivers 214, which include radio frequency (RF) front-ends 216 andantennae 218. Radio hardware 212 may be communicatively coupled toprocessor(s) 202 and to memory 204. Sensing hardware 220 includessensing RF front-end 222 and sensing antenna 224. Sensing hardware 220may be configured to probe for and/or sense available physical frequencybands, such as by looking for TV signals. Sensing RF front-end 222 andsensing antenna 224 may be the same or different from RF front-ends 216and antennae 218.

The memory 204 may store program instructions that are loadable andexecutable on the processor(s) 202, as well as data generated duringexecution of, and/or usable in conjunction with, these programs. In theillustrated example, memory 204 stores an operation system 226, usermode software services 228, and kernel 230 (which may be part ofoperating system 226). The operating system 226 provides basic systemfunctionality of white space base station 200 and, among other things,provides for operation of the other programs and modules of white spacebase station 200. User mode software services 228 include a spectrummanager 232, a base station service 234 configured to provide wirelesstransmission service to wireless clients such a geo-location service andweb caching, access connection manager 236 configured to control useraccess rights and connectivity, and security manager 238 configured toprovide security services of white space base station 200 such as accesscontrol lists, authentication, wireless encryption, and so forth.

Kernel 230 includes a communication module 240. Communication module 240includes a spectrum virtualization module 242 configured to interfacewith radio hardware 212 to transmit radio signals to one or more clientdevices. Spectrum virtualization module 242 is also configured tointerface with one or more wireless transmission protocols 244-M, eachincluding a MAC-M layer and PHY-M layer. As described with reference toFIG. 1, for example, spectrum virtualization layer 242 is configured topresent a virtual baseband to the PHY layers of wireless transmissionprotocols 244-M, shape outgoing virtual baseband signals to physicalbaseband signals for transmission on radio hardware 212 and to inverseshape incoming physical baseband signals for handling by the PHY layers.This allows conventional PHY protocols to be used for white spacetransmission without modification.

Spectrum manager 232 includes an availability module 246 configured torequest and receive information regarding available white space physicaltransmission frequency bands. Availability module 246 may be configuredto query one or both of sensing hardware 220 and/or a white space finderservice for the available frequency bands. Spectrum manager 232 alsoincludes policy module 248 that contains one or more policies such asregulatory policies or transmission requirements. Non-limiting examplesof regulatory policies include guard bands requirements, power maskrequirements, times that white space frequency bands are available,acceptable transmission power level ranges, and so forth.

The transmission requirements in policy module 248 may includerequirements designated by various standards, protocols, specificationsand so forth. Non-limiting examples of wireless protocol specificationtransmission requirements include bandwidth requirements, single ormulticarrier modulation requirements, power transmission levelrequirements, duplex/simplex transmission requirements, variableupload/download transmission requirements, and so forth.

Spectrum manager 232 also includes decision module 250 that may beconfigured to compare the available physical transmission frequencybands with the policies (such as regulatory policies and/or transmissionrequirements) in policy module 248 in order to select appropriate onesof the locally-available, non-interfering physical transmissionfrequency bands that will allow white space base station 200 to conformto the policies. Decision module 250 is also configured to map theselected ones of the available physical transmission frequency bands tothe virtual frequency bands employed by spectrum virtualization module242 and wireless transmission protocols 244. Decision module 250 isconfigured to make the selection based on a comparison of the policiesto the available physical transmission frequency bands. For example,decision module 250 may consider bandwidth requirements of the wirelesstransmission protocols 244 and guard band requirements of the regulatorypolicies in selecting ones of the available physical transmissionfrequency bands for transmission by white space base station 200.

Decision module 250 is configured, in embodiments, to map multiple onesof the selected physical frequency bands to a single virtual spectrumband. This may occur, for example, where no single frequency band isavailable to meet the bandwidth or other requirements of one or more ofthe wireless transmission protocols 244-M. The multiple ones of theselected physical frequency bands may be non-contiguous physicalfrequency bands. Decision module 250 may also map a single physicalfrequency band to one or more virtual frequency bands. Decision module250 may be configured to map virtual frequency bands associated withmultiple ones of wireless transmission protocols 244-M to one or morephysical transmission frequency bands. This allows white space basestation 200 to support multiple simultaneous white space transmissions,to multiple white space clients, utilizing different ones of wirelesstransmission protocols 244-M. One or more of radio transceivers 214 maybe utilized to perform the multiple simultaneous transmissions. Someembodiments may have different numbers of radio transceivers 214 andwireless transmission protocols 244. Or stated another way, N (thenumber of radio transceivers) does not necessarily equal M (the numberof wireless transmission protocols supported by communication module240).

As noted above, availability module 246 may forward the location ofwhite space base station 200 to a service, such as a white space finderservice. The location of white space base station 200 may be determinedby location hardware 252, which may be operatively coupled toprocessor(s) 202 and memory 204. Non-limiting examples of locationhardware 252 include global positioning system (GPS) receivers, cellulartelephone receivers, or others. Alternatively, availability module 246may be configured to forward manually configured location information.Such manually configured location information may include coordinatessuch as longitude and latitude or other coordinate types, an addresswhere white space base station is deployed, or other locationinformation. In other alternative embodiments, availability module 246may be configured to send an identifier of white space base station 200,such as an IP address, a unique identification number, a MAC address, orother to a white space finder service. The white space finder servicemay be configured to determine the location of the white space basestation 200 based on the unique identifier, such as for example wherethe location of white space base station 200 has been previouslyprovided to the white space finder service.

Although white space base station 200 has been described as employingwhite space networking, base stations according to embodiments may alsoemploy other DSA networking types.

Example White Space Finder Service

FIG. 3 is a block diagram of an example white space finder service 300.White space finder service 300 may be configured as any suitablecomputing device(s) capable of implementing a white space finderservice. According to various non-limiting examples, suitable computingdevices may include personal computers (PCs), servers, server farms,datacenters, combinations of these, or any other computing device(s)capable of storing and executing all or part of the white space finderservice. White space finder service 300 may be implemented as an ActiveServer Page (ASP) .Net Web Service.

In one example configuration, white space finder service comprises oneor more processors 302 and memory 304. White space finder service 300may also contain communication connection(s) 306 that allowcommunications with various devices such as for example a white spacebase station. The white space finder service 300 may also include one ormore input devices 308, such as a keyboard, mouse, pen, voice inputdevice, touch input device, etc., and one or more output devices 310,such as a display, speakers, printer, etc. coupled communicatively tothe processor(s) 302 and memory 304.

The memory 304 may store program instructions that are loadable andexecutable on the processor(s) 302, as well as data generated duringexecution of, and/or usable in conjunction with, these programs. In theillustrated example, memory 304 stores an operating system 312 toprovide basic system functionality of white space finder service 300and, among other things, provides for operation of the other programsand modules of white space finder service 300.

Memory 304 includes a reception module 314 configured to receive, fromone or more white space base stations, location information of the whitespace base stations along with requests for available physical frequencybands for wireless transmission by the white space base stations.Propagation module 316 is configured to determine one or more geographicareas over which wireless transmissions by one or more primary users arelikely to propagate. This determination is based at least on terraindata 318 associated with the locations of one or more primary users(such as television transmitters or licensed wireless microphone users)that are near a white space base station. Interference determinationmodule 320 is configured to determine, based on the location of thewhite space base station and the modeled geographic propagation areas,one or more locally available, non-interfering transmission frequencyranges that will allow the white space base station to transmitnon-interfering signals in its local area. For example, if the whitespace base station is within a modeled transmission propagation area ofa particular primary user, interference determination module 320 maydetermine that the white space base station would interfere with thatparticular primary user if the white space base station were to transmiton the same frequency as that particular primary user. Interferencedetermination module 320 is configured to select non-interferingtransmission frequency ranges from frequency channel data 324. Thepropagation area and interference determinations may be modeled, inembodiments, using one of various propagation models such as theLongley-Rice radio signal propagation model. Send module 326 isconfigured to transmit, to the secondary wireless device, dataindicative of the one or more available transmission frequency ranges.Such data may be frequency ranges, center frequencies and bandwidths,channel identifiers, and so forth.

Embodiments may support voluntary provision of spectrum by primary usersfor use in white space transmissions. Volunteer module 328 is configuredto receive voluntary donations of spectrum from donors and to make thatspectrum available to white space finder service 300, such as by addingthe volunteered spectrum to frequency channel data 324. Such spectrummay be television transmission spectrum, or other spectrum. Revocationmodule 330 is configured to receive revocations of voluntarily providedspectrum, and to forward revocations of the one or more physicaltransmission frequency bands to the white space base station.

Although white space finder service 300 has been described as providingavailable “white space” frequency bands, finder services according toembodiments may also provide lists of frequency bands usable by otherDSA networking types.

Use of Location Information

As noted above, location information of a white space base station, suchas white space base station 102 illustrated in FIG. 1, or white spacebase station 200 illustrated in FIG. 2, may be used to determine one ormore frequency ranges for white space transmissions. Maintaining privateinformation is important. Therefore, some embodiments take appropriatesteps to ensure that an individual cannot be identified from his or herlocation information. For example, any personally identifyinginformation such as names, usernames, passwords, social securitynumbers, account numbers, and so forth may be omitted from the requestfor available white space sent by white space base stations.Furthermore, white space finder services—such as white space finderservice 104 illustrated in FIG. 1 and white space finder service 300illustrated in FIG. 3—may be kept in a secure location and protectedagainst unauthorized access using appropriate measures such asencryption and network access controls. Location information may also beroutinely purged. Moreover, users may be provided with notice that theirlocation information is being transmitted, along with information on howtheir location information will be used. Furthermore, users may beallowed to provide either opt-in or opt-out consent. With opt-inconsent, the user takes an affirmative action before his or her locationinformation is used or transmitted. With opt-out consent, the user takesan affirmative action to prevent the use or transmission of his or herlocation data before that data is collected, transmitted, or used.

Example Process for Frequency Selection by a White Space Base Station

FIG. 4 is a flowchart showing an example process of frequency selectionby a white space base station. The process of FIG. 4 may, but may not,be implemented in environment 100 of FIG. 1 and/or using white spacebase station 200 of FIG. 2. Some portions of the processes shown in FIG.4 may be implemented by computer-executable instructions. Generally,computer-executable instructions can include routines, programs,objects, components, data structures, procedures, modules, functions,and the like that perform particular functions or that implementparticular abstract data types. The processes can also be practiced in adistributed computing environment where functions are performed byremote processing devices that are linked through a communicationnetwork. In a distributed computing environment, computer-executableinstructions may be located in local and/or remote computer storagemedia, including memory storage devices.

The exemplary processes are illustrated as a collection of blocks in alogical flow graph representing a sequence of operations that can beimplemented in hardware, software, firmware, or a combination thereof.The order in which the processes are described is not intended to beconstrued as a limitation, and any number of the described processblocks can be combined in any order to implement the process, oralternate processes according to various embodiments of the presentdisclosure. Additionally, individual blocks may be omitted from theprocess without departing from the spirit and scope of the subjectmatter described herein. In the context of software, the blocksrepresent one or more computer instructions that, when executed by oneor more processors, perform the recited operations.

Referring back to FIG. 4, process 400 includes receipt, by a white spacedevice, of one or more non-interfering physical transmission frequencyranges that are available at a location of the white space device, block402. The white space base station may compare the available physicaltransmission frequency ranges to one or more policies, block 404. Suchpolicies may include requirements of a wireless transmission protocol orregulatory requirements associated with the physical transmissionfrequency ranges. Non-limiting examples of policies include guard bandrequirements, power mask requirements, one or more of bandwidthrequirements of the wireless transmission protocol, requirements forsingle or multicarrier modulation, power transmission masks, duplex orsimplex transmission requirements, variable upload and downloadbandwidth requirements, and so forth. The white space base stationselects some or all of the available physical transmission frequencyranges based on the comparison, block 406. The white space base stationmaps the selected physical transmission frequency ranges to one or morevirtual transmission frequency ranges of the wireless transmissionprotocol, block 408.

During transmission, a PHY layer associated with a wireless transmissionprotocol may modulate a data stream on a virtual baseband according to avirtual frequency range of the wireless transmission protocol, block410. The virtual frequency range may be one of several frequency rangesset or established by the wireless transmission protocol for wirelesstransmissions according to the wireless transmission protocol.

A spectrum virtualization module of the white space base station mayshape the virtual baseband signals according to the selected physicaltransmission frequency ranges to create physical baseband signals, block412. Radio hardware of the white space base station may transmit radiofrequency signals according to the physical baseband signals, block 414.Such transmission may include Digital-to-Analog Conversion (DAC) of thephysical baseband signals to analog signals for transmission by theradio hardware.

During reception of white space transmissions from a white space clientdevice, the radio hardware may receive radio frequency signals on theselected physical transmission frequency ranges, block 416. The radiohardware may perform Analog-to-Digital Conversion (ADC) of the receivedradio frequency signals to generate physical baseband signals, block418. The spectrum virtualization module of the white space base stationinverse shapes the received physical baseband signals into virtualbaseband signals, according to the virtual frequency ranges, block 420.The virtual baseband signals are then demodulated by the wirelesstransmission protocol PHY layer, block 422. The PHY layer extracts theunderlying digital information and passes the digital information tohigher-level layers of the protocol stack.

Ongoing transmission and reception may proceed in this fashion until arevocation of one or more of the selected physical transmissionfrequency ranges is received, block 424. Once a revocation is received,an availability module of a spectrum manager of the white space devicerequests and receives a new list of available physical transmissionfrequency ranges, block 402. Alternatively, the decision module of thewhite space device may select another of the previously received list ofavailable physical transmission frequency ranges that have not beenrevoked, block 404.

By selecting and mapping the physical transmission frequency ranges tothe virtual frequency ranges, the white space devices adhere to thenon-interference principal of white space transmission. In variousembodiments, the white space finder service provides a list of availableand non-interfering space frequency ranges for use by the white spacebase station, as is described in the following section.

Example Process for Location-Specific Determination of Non-InterferingFrequencies by a White Space Finder Service

FIG. 5 is a flowchart showing an example process for determination oflocation-specific, non-interfering white space frequency ranges by awhite-space finder service. The process of FIG. 5 may, but may not, beimplemented in environment 100 of FIG. 1 and/or using white space finderservice 200 of FIG. 3. Some portions of the processes shown in FIG. 5may be implemented by computer-executable instructions. Generally,computer-executable instructions can include routines, programs,objects, components, data structures, procedures, modules, functions,and the like that perform particular functions or that implementparticular abstract data types. The processes can also be practiced in adistributed computing environment where functions are performed byremote processing devices that are linked through a communicationnetwork. In a distributed computing environment, computer-executableinstructions may be located in local and/or remote computer storagemedia, including memory storage devices.

The exemplary processes are illustrated as a collection of blocks in alogical flow graph representing a sequence of operations that can beimplemented in hardware, software, firmware, or a combination thereof.The order in which the processes are described is not intended to beconstrued as a limitation, and any number of the described processblocks can be combined in any order to implement the process, oralternate processes according to various embodiments of the presentdisclosure. Additionally, individual blocks may be omitted from theprocess without departing from the spirit and scope of the subjectmatter described herein. In the context of software, the blocksrepresent one or more computer instructions that, when executed by oneor more processors, perform the recited operations.

Referring back to FIG. 5, process 500 includes receipt of messagesindicating voluntary donations of spectrum to be made available in oneor more areas covered by the white space finder service, block 502. Areception module receives from a white space base station a request foravailable physical transmission frequency ranges, block 504. The requestmay be accompanied by location information of the white space basestation, block 506. Alternatively, an identifier of the white space basestation may accompany the request and the white space finder service mayretrieve previously stored information about the location of the whitespace base station based on the identifier, which may be in the form oflatitude and longitude, global positioning system coordinates, streetaddresses, or other location information. The identifier may include anIP address, a unique identification number, an email address, or MACaddress, or other identifying information.

The white space finder service may retrieve terrain data associated withthe location of the white space base station, block 508. The white spacefinder service determines, based on propagation modeling and locationsof one or more primary users (such as television signal transmitters), ageographic area over which the primary users' transmissions are likelyto propagate, block 510. The white space finder service will determine,based on the location of the white space base station, whether the whitespace base station transmissions would potentially interfere with theprimary user transmission devices, block 512. For example, if the whitespace base station is located within the propagation area for aparticular primary user, then the white space finder may determine thatthe white space base station may interfere with the particular primaryuser if the white space base station were to transmit on the samefrequency as the particular primary user. One or more non-interferingphysical transmission frequency ranges are determined and sent to thewhite space base station, block 514. For example, if the white spacebase station is located within a propagation area of a particularprimary user, then the white space finder may determine that it ispermissible for the white space base station to transmit on otherfrequencies besides the frequency ranges that the particular primaryuser transmits on.

As noted above, white space finder service may be configured to acceptvoluntary provision of spectrum by holders, licensees, or owners of suchspectrum for use in white space transmissions in one or moregeographical areas. Such voluntary provision may be limited, such as forexample to certain times of day, certain durations, certain dates, andso forth. The white space finder service may therefore determine whethera limit, such as time expiration, has passed, block 516. If so, arevocation of the physical transmission frequency ranges is sent to thewhite space base station, block 518.

Also, the holder, licensee, or owner of the spectrum may revoke the useof the spectrum in one or more geographical areas, block 520, therebyprompting the white space finder service to transmit a revocation to thewhite space base station.

Although process 500 has been described as providing available “whitespace” frequency bands, embodiments may also provide lists of frequencybands usable by other DSA networking types.

Terrain Data and Propagation Modeling Illustration

FIG. 6 illustrates a local geographic area of a white space basestation, and a visible depiction of the modeled propagation area of itstransmission signal. As noted above, a white space finder service modelsthe propagation area of one or more primary user transmitters within alocal area of the white space base station. This is done in order todetermine whether the white space base station's transmissions wouldpotentially interfere with the primary user transmitters. Such modelingmay exist as a digital representation within memory of the white spacefinder service. As such, the white space finder service need not,although it may, generate and display a visible depiction of the modeledpropagation area as illustrated in FIG. 6. FIG. 6 is presented hereinprimarily for the sake of illustration.

Referring to FIG. 6, terrain map 600 illustrates a local geographic areanear white space base station 602. As noted above, a white space finderservice may receive location information regarding the location of whitespace base station 602 and utilize terrain data to determine whether thewhite space base station's transmission signals might potentiallyinterfere with primary users. In the illustrative example shown in FIG.6, the terrain data may indicate the presence of hill 604, woods 606,and buildings 608. Based on these and other terrain features, apropagation module of the white space finder service may determinepropagation areas over which transmission signals from various primaryuser devices are likely to propagate. Hill 604, woods 606, and buildings608 may shorten the distance of transmission signals in certaindirections.

Various primary user transmission devices 610-616 are present on terrainmap 600, and are near to white space base station 602. One of them,primary user transmission device 616, is shown along with propagationarea 610, which is the geographic area that transmissions from primaryuser transmission device 616 are likely to propagate, based for exampleon the presence of hill 604, woods 606, and buildings 608, and asdetermined using propagation modeling. Thus, the white space finderservice may select a physical transmission frequency range that is notused by primary user transmission device 616 for white spacetransmission by white space base station 602. Thus, even though whitespace base station 602 is within propagation area 610, transmissions bywhite space base station 602 may be determined to be non-interferingwith primary user transmission device 616 because the two utilizedifferent frequency ranges. At the same time, white space base station602 may be provided with frequency ranges that are also used by primaryuser transmission device 610, 612, and/or 614 (or other frequency rangesutilized by none of the primary user transmission devices). White spacebase station 602 may be determined to be sufficiently unlikely tointerfere with transmissions from primary user transmission devices 610,612, and 614—even if white space base station 602 utilizes the sametransmission frequencies as those devices—because white space basestation 602 is not within the modeled transmission propagation areas ofthose devices.

Spectrum Virtualization Environment

FIG. 7 illustrates a transmission environment including a base stationand wireless clients configured to use spectrum virtualization.Transmission environment 700 includes base station 702, wireless client704, and wireless client 706. Base station 702 may be the same ordifferent than white space base station 102 in FIG. 1 and/or white spacebase station 200 in FIG. 2. Base station 702 may be implemented onvarious suitable computing device types that are capable of implementinga base station. Suitable computing device or devices may include, or bepart of, one or more personal computers, servers, server farms,datacenters, combinations of these, or any other computing device(s)capable of storing and executing all or part of a base station service.Various portions of base station 702 may also be implemented as hardwarelogic, such as an application specific integrated circuit (ASIC) or asone of various programmable or reprogrammable processor types such as afield programmable gate array (FPGA).

Wireless client 704 and wireless client 706 may be implemented onvarious suitable computing device types that are capable of implementinga wireless client. Suitable computing device or devices may include, orbe part of, one or more personal computers, servers, server farms,datacenters, combinations of these, or any other computing device(s)capable of storing and executing all or part of a wireless client.Various portions of wireless clients 704 and 706 may be implemented ashardware logic, such as an application specific integrated circuit(ASIC) or as one of various programmable or reprogrammable processortypes such as a field programmable gate array (FPGA).

Base station 702 includes memory 708 and one or more processors 710. Thememory 708 may store program instructions that are loadable andexecutable on the processor(s) 710, as well as data generated duringexecution of, and/or usable in conjunction with, these programs. Basestation 702 also includes radio hardware 712, which may include a radiofrequency (RF) front-end and antennae.

Memory 708 includes wireless protocols 714-A and 714-B. Wirelessprotocol 714-A includes MAC-A and PHY-A, and wireless protocol 714-Bincludes MAC-B and PHY-B. Non-limiting examples of wireless protocols714-A and 714-B include Wi-Fi®, protocols within the 802.11 suite ofprotocols, and ZigBee.

Memory 708 also includes spectrum virtualization module 716, configuredto implement a spectrum virtualization layer. Spectrum virtualizationmodule 716 is configured to, among other things, map virtual frequencybands to physical frequency bands, and to interface between radiohardware 712 and wireless protocols 714-A and 714-B.

Wireless client 704 includes memory 718 and one or more processors 720.The memory 718 may store program instructions that are loadable andexecutable on the processor(s) 720, as well as data generated duringexecution of, and/or usable in conjunction with, these programs.Wireless client 704 also includes radio hardware 722, which may includea radio frequency (RF) front-end and antennae.

Memory 718 includes wireless protocol 714-A, for communication with basestation 702. Memory 718 also includes spectrum virtualization module724, configured to implement a spectrum virtualization layer. Spectrumvirtualization module 724 is configured to, among other things, mapvirtual frequency bands to physical frequency bands, and to interfacebetween radio hardware 722 and wireless protocol 714-A.

Wireless client 706 includes memory 726 and one or more processors 728.The memory 726 may store program instructions that are loadable andexecutable on the processor(s) 728, as well as data generated duringexecution of, and/or usable in conjunction with, these programs.Wireless client 706 also includes radio hardware 730, which may includea radio frequency (RF) front-end and antennae.

Memory 726 includes wireless protocol 714-B, for communication with basestation 702. Memory 726 also includes spectrum virtualization module732, configured to implement a spectrum virtualization layer. Spectrumvirtualization module 732 is configured to, among other things, mapvirtual frequency bands to physical frequency, and to interface betweenradio hardware 730 and wireless protocol 714-B.

As opposed to a conventional wireless system—where PHY layers interfacedirectly with an RF front-end—embodiments of the present disclosureemploy spectrum virtualization modules (such as spectrum virtualizationmodules 716, 724, and 732 in FIG. 7) to create an intermediate interfacebetween the PHY layers and a RF front-end. This interface can be thoughtof as level 0.5 of the Open Systems Interconnections (OSI) model,directly below layer 1 (the Physical Layer, abbreviated “PHY” herein”).Reference to the OSI model, and to various layers within the OSI model,are not meant to imply that embodiments are compatible only with wiredor wireless transmission protocols that conform to the OSI model.Rather, the OSI model and its various layers are referenced herein forthe sake of discussion.

When transmitting to wireless client 704, spectrum virtualization module716 of base station 702 is configured to accept virtual baseband signalsmodulated by wireless protocol 714-A, shape the virtual basebandmodulated signals, and map them to a physical baseband according to aspectrum map. Spectrum virtualization module 716 is configured to passthe shaped and mapped modulated signals to radio hardware 712 fortransmission as analog signals on the physical frequency spectrum towireless client 704.

Radio hardware 722 of wireless client 704 is configured to select thephysical frequency spectrum, receive the transmitted analog signals,digitize them, and pass them to spectrum virtualization module 724.Spectrum virtualization module 724 is configured to inverse shape andmap the physical baseband modulated signals into virtual basebandmodulated signals. Wireless protocol 714-A of wireless client 704accepts the inverse shaped modulated virtual baseband signals,demodulates them, and extracts the digital data contained within forprocessing by higher-level layers of the protocol stack.

Wireless client 706 is configured to perform functions that are similarto the functions that wireless client 704 is configured to perform. Butwireless client 706 employs wireless protocol 714-B rather than wirelessprotocol 714-A. In alternate embodiments, different wireless clientscould utilize the same wireless protocols, and different wirelessclients could utilize the same physical transmission bands as oneanother.

Spectrum Virtualization Overview

Various embodiments of the present disclosure “virtualize” a non-variantspectrum band out of the dynamic changing physical spectrum allocationin dynamic spectrum access (DSA) networks. (White space networks areexamples of DSA networks). Embodiments of the present disclosure supportvarious wireless PHY protocols without the need to change the design ofthose various wireless PHY protocols. Embodiments accomplish this byusing a spectrum virtualization layer situated logically below thewireless PHY layer to perform baseband processing on the basebandsignals that are output by the PHY layer. The spectrum virtualizationlayer intercepts and rewrites digital signals that pass between thebaseband presented by the PHY layer and the radio frequency (RF)front-end hardware—in both send and receives directions—to hide thedynamically changing spectrum allocation of the DSA network and tocreate the effect of a fixed spectrum from the perspective of the PHYprotocol.

Next, a conventional radio transceiver and conventional wirelessprotocol PHY layer will be described. That description will be followedby a description of how spectrum virtualization layers according toembodiments that interface with the PHY layer and the radio transceiver.

A conventional radio transceiver includes a radio frequency (RF)front-end and a baseband processing unit. In conventional radio designs,baseband processing is generally performed in the digital domain withdigital signal samples, and the RF front-end mainly contains analogradio circuitry. Thus, analog-to-digital conversion (ADC) anddigital-to-analog conversion (DAC) form the nature of the interfacebetween the conventional baseband unit and the RF front-end. Theconventional baseband unit performs digital baseband modulation oninformation bits to create digital baseband waveforms, and vice versa.Digital modulation maps a binary sequence to segments of digitalwaveform samples. These segments are called symbols. At the receiverside, the symbols are demodulated to retrieve the embedded binaryinformation. The RF front-end converts the digital baseband signals (thesymbols) into analog radio signals and transmits them. During reception,the RF front-end selects the radio frequency signal, down-converts thesignals, and digitizes the signals to form digital baseband samples.

Different conventional wireless PHY protocols use different modulationtechniques. Generally speaking, baseband modulation can be classifiedinto single carrier modulation (SCM) and multi-carrier modulation (MCM).ZigBee, 802.11b and Wideband Code Division Multiple Access (WCDMA) areexamples of single carrier systems. Various high-speed wireless systemssuch as 802.11a/g and Long Term Evolution (LTE) use multi-carriermodulation. In addition to being classifiable by their modulationtechniques, conventional wireless PHY protocols can also be classifiedby how they handle multi-path fading. For example, rake-receiver iscommonly used for SCM signals that have been spread. But protocols thatutilize MCM often rely on cyclic-prefixes (CP) to remove the impact ofmulti-path fading. The fundamental tradeoffs in various conventionalwireless PHY design choices—such as MCM versus SCM, and Rake-receiverversus CP—make it unlikely that a single PHY layer protocol could beadopted for all wireless applications.

A spectrum virtualization layer, according to various embodiments of thepresent disclosure, is one way to support multiple conventional PHYlayers in a DSA network in order to maintain flexibility for variouswireless transmission bands. The interworking between a spectrumvirtualization layer according to embodiments and a radio frequencyfront-end will now be described.

FIG. 8 illustrates the interworking between a radio frequency front-end,the spectrum virtualization layer, and a physical layer duringtransmission between a sender and a receiver. Transmission 800 isbetween sender 802 and receiver 804. Sender 802 and receiver 804 bothemploy wireless PHY protocol 806, which may be one of various PHYprotocols such as are described within this Detailed Description. Sender802 and/or receiver 804 may also employ one or more other PHY protocols.Sender 802 may be a base station such as base station 702 in FIG. 7, awireless client, such as wireless clients 704 and 706 in FIG. 7, oranother device type. Sender 802 employs RF front-end 808, and receiver804 employs RF front-end 810. Sender 802 employs spectrum virtualizationlayer (SVL) 812, and receiver 804 employs SVL 814.

Referring to sender 802, SVL 812 maps a virtual baseband associated witha “virtual” frequency band or spectrum to one or more physical basebands(shown as “phys b-band” in FIG. 8) that are associated with a physicalfrequency band or spectrum. The virtual frequency band may be a fixedspectrum (or one of several fixed spectrums) designated by PHY 806,while the physical baseband may be according to one of severaldynamically allocated frequency bands, such as in a white space networkor, more generally, a DSA network. SVL 812 is configured to map andshape virtual baseband signals to one or more physical baseband signals.RF front-end 808 is configured to convert the digital physical basebandsignals to analog signals, and to transmit them on one or more antennae(not shown).

RF front-end 810 of receiver 804 is configured to receive the analogsignals transmitted by RF front-end 808, and to convert them intodigital samples to form one or more physical basebands. SVL 814 isconfigured to map and inverse shape the physical baseband signals tovirtual baseband signals, before passing them along to PHY 806 ofreceiver 804. PHY 806 of receiver 804 demodulates the virtual basebandsignals and extracts the underlying digital data sent by sender 802. Inthis way, SVL 812 presents PHY 806 of sender 802 with a virtual basebandaccording to a fixed frequency (which may be specified by PHY 806), andSVL 814 presents PHY 806 of receiver 804 with a virtual baseband,according to the same fixed frequency. Thus PHY 806 of sender 802 andPHY 806 of receiver 804 communicate with one another as if sender 802and receiver 804 were transmitting on the fixed frequency. But SVLs 812and 814 make it possible to transmit using one or more physicalfrequency bands that have been allocated dynamically for thetransmission. The dynamically allocated physical frequency bands may bedifferent from the fixed frequency employed by PHY 806.

Both sender 802 and receiver 804 may be capable of sending andreceiving. They are referred to as “sender” and “receiver” in FIG. 8 forthe sake of description. Thus, transmissions can be sent from receiver804, via SVL 814 and RF front-end 810, to sender 802 via RF front-end808 and SVL 812.

A spectrum virtualization layer (such as SVL 812 and SVL 814 of FIG. 8)may be configured to create a bridge between PHY protocols and thedynamic baseband in a DSA network (such as a white space network). PHYprotocols are usually designed for a fixed frequency transmission, andDSA networks may have a time and space-varying spectrum configuration.The dynamic baseband in a DSA network may also be wider or narrower thanthe fixed frequency baseband of the PHY protocols. The SVL allows thefixed frequency band of the PHY protocols to be mapped to a narrower orwider frequency band.

Another function of the spectrum virtualization layer is to decouple theconnection between the PHY protocol and the RF front-end, and to add alayer of indirection. The virtual baseband and the physical basebanddiffer in the sense that one is fixed and specified by PHY protocoldesign, and the other is dynamic and determined by a DSA allocationmethod (such as for example by the processes employed by white spacefinder services and spectrum managers in accordance with variousembodiments of the present disclosure). At the sender side, the PHYprotocol generates digital waveforms as if it were connected to an RFfront-end. The SVL layer intercepts these samples and reshapes them intoa different waveform shapes so that, when the RF front-end transmits thetransformed waveform shapes, the resultant radio signals match thedynamic spectrum allocation of the DSA or white space network. At thereceiver side, the SVL performs the inverse reshaping operation on thephysical baseband samples to recover the original digital waveformshapes for the PHY layer. As shown in the example of FIG. 8, arelatively wide virtual baseband is reshaped into two relatively narrowphysical basebands during transmission. During reception (such as byreceiver 804), the SVL inverse reshapes the two relatively narrowphysical basebands into the one relatively wide virtual baseband.

Spectrum Virtualization Architecture

FIG. 9 illustrates a block diagram of a spectrum virtualization layerarchitecture 900. Portions of architecture 900 may be implemented as asoftware module configured to execute on one or more processors, as isdescribed elsewhere within this Detailed Description. In alternativeembodiments, architecture 900 may be implemented on an ApplicationSpecific Integrated Circuit (ASIC), or on one of various programmable orreprogrammable processor types, such as Field Programmable Gate Arrays(FPGA) or others. Architecture 900 may be employed by a wireless basestation, such as white space base station 102 of FIG. 1, white spacebase station 200 of FIG. 2, and/or base station 702 of FIG. 7.Architecture 900 may also be employed on a wireless client, such aswireless clients 704 and 706 of FIG. 7.

SVL 902 provides a virtual baseband to one or more PHY 904 and isconfigured to dynamically translate the signals between a virtualbaseband and a physical baseband provided by one or more RF front-ends906. The width of the virtual baseband is specified by one or more PHY904, such as for example during an initialization stage. The one or morePHY 904 may be part of a wireless transmission protocol that alsospecifies a media access control (MAC) layer, as shown in FIG. 9.

SVL 902 maintains a spectrum map 908 showing the mapping between thevirtual baseband and the physical spectrum bands. The mapping containedin spectrum map 908 is flexible. For example, spectrum map 908 may mapthe virtual baseband to a physical spectrum band having the same width(e.g., the mapping of virtual spectrum band VS1 to an equal-sizedphysical band). Alternatively, spectrum map 908 may map the virtualbaseband to a narrower contiguous physical band, or severalnon-contiguous physical bands (e.g., the mapping of virtual spectrumbands VS2 and VS3 to differently sized physical bands). In otherembodiments, spectrum map 908 may map the virtual baseband to a broadercontiguous physical band, or sever non-contiguous physical bands thattogether are larger than the virtual baseband.

Spectrum allocation is controlled by spectrum manager 910. Spectrummanager 910 may be the same as or different than spectrum manager 114 inFIG. 1 and/or spectrum manager 232 in FIG. 2. Spectrum manager 910 isconfigured to monitor the current spectrum usage (e.g., by sensing orquerying a database such as a white space finder service), to allocateavailable physical spectrum bands for one of PHY 904 based on variouspolicies, and to update the spectrum map 908 in SVL 902.

The one or more reshapers 912 are configured to translate signals frombaseband to physical bands, and vice versa. The one or more reshapersare configured to perform signal translation without reference to themodulation scheme employed by the one or more PHY 904. In embodiments,one or more reshapers 912 are configured to employ digital signalprocessing algorithms that operate on general baseband waveforms.

The one or more reshapers 912 may be transparent to one or more PHY 904.For example, although the reshaping operation may change the basebandwaveform in some way, the one or more PHY 904 may treat this distortionas if it were due to normal wireless channel fading. This allows the oneor more PHY 904 to model the distortion caused by the reshapingoperation by an equivalent multipath fading channel, and to handle anydistortion caused by the reshaping operation using equalizationmechanisms already available to the one or more PHY 904.

After reshaping, baseband signals are converted to physical basebandsignals. Physical baseband signals from multiple ones of PHY 904 may bemixed (added) together by mixers 914 before they are sent to RFfront-ends 906.

When receiving, the incoming signals are passed to splitters 916, whichcontain a matched filter for the one or more PHY 904 based on spectrummap 908. The filtered physical band signals are fed to the reshapers912, which are configured to perform inverse reshaping operations torecover the virtual baseband signals. Virtual baseband signals are sentto the one or more PHY 904. The PHY 904 are configured to demodulate thevirtual baseband signals and to obtain the underlying binaryinformation.

Conceptually, SVL 902 virtualizes the RF front-ends 906 for each of theone or more PHY 904. SVL 902 is configured to flexibly map differentones of PHY 904 to different ones of RF front-ends 906. Also, SVL 902 isconfigured to multiplex several ones of PHY 904 onto a single one of RFfront-ends 906. RF front-end virtualization allows multiple ones of PHY904 to share a common one of RF front-ends 906. RF front-endvirtualization may therefore reduce the bandwidth resources needed formulti-radio integration, thereby requiring less space and energy, andpossibly resulting in lower-cost mobile devices.

FIG. 10 illustrates a spectrum virtualization layer configured to mapdifferent wireless transmission protocols to different radio front-ends.SVL 1002 presents a virtual baseband to PHY 1, PHY 2, and PHY 3. SVL1002 also presents a physical baseband to RF Front-end 1 and RFFront-end 2 as shown in FIG. 10. SVL 1002 is shown in FIG. 10 mappingreshaped modulated baseband signals from PHY 1 to RF Front-end 1. SVL1002 is also—in the configuration shown in FIG. 10—shown mixing reshapedmodulated baseband signals from PHY 2 and PHY 3 together, and mappingthose mixed signals to RF Front-end 2. Such mapping and mixing may be,for example, based on a spectrum map as is described elsewhere withinthis Detailed Description.

Spectrum Virtualization Layer Interfaces

Spectrum virtualization layers according to various embodiments defineinterfaces. FIG. 11 is a flow diagram showing an example process 1100for interface calls to a spectrum virtualization layer. The process ofFIG. 11 may, but may not, be implemented in, or in conjunction with, thecommunication module 128 in FIG. 1, communication module 240 of FIG. 2,transmission 800 of FIG. 8, environment 700 of FIG. 7, architecture 900of FIG. 9, and/or SVL 1002 and PHY layers shown in FIG. 10.

Some portions of the processes shown in FIG. 11 may be implemented bycomputer-executable instructions. Generally, computer-executableinstructions can include routines, programs, objects, components, datastructures, procedures, modules, functions, and the like that performparticular functions or that implement particular abstract data types.The processes can also be practiced in a distributed computingenvironment where functions are performed by remote processing devicesthat are linked through a communication network. In a distributedcomputing environment, computer-executable instructions may be locatedin local and/or remote computer storage media, including memory storagedevices.

The exemplary processes are illustrated as a collection of blocks in alogical flow graph representing a sequence of operations that can beimplemented in hardware, software, firmware, or a combination thereof.The order in which the processes are described is not intended to beconstrued as a limitation, and any number of the described processblocks can be combined in any order to implement the process, oralternate processes according to various embodiments of the presentdisclosure. Additionally, individual blocks may be omitted from theprocess without departing from the spirit and scope of the subjectmatter described herein. In the context of software, the blocksrepresent one or more computer instructions that, when executed by oneor more processors, perform the recited operations.

Referring back to FIG. 11, a wireless PHY protocol registers with theSVL before it sends and receives signal samples, block 1102. Duringregistration, the wireless PHY protocol defines a virtual spectrum band,a desired bandwidth for the baseband, and one or more over-sampleparameters. The over-sample parameters, together with the desiredbandwidth, determine the sampling rate of the baseband. The samplingrate may be at least twice the bandwidth, in order to satisfy Nyquistcriteria. It is possible for a wireless PHY to specify an over-samplingrate greater than two, which may provide better performance but incurgreater computational cost. This greater computational cost results fromthe additional samples that are processed in a given interval whenover-sampling is used. The wireless PHY will also, during registration,define a number of sub-carriers used in multi-carrier modulation. Forsingle carrier modulation, this number will be equal to one.

Another parameter specified during registration describes the sorts ofreshape operations to be performed on the virtual baseband signals ofthe PHY. This parameter will work together with the spectrum manager todetermine mapping between the virtual baseband and the physical spectrumbands. Some non-limiting examples include parameters that indicate thatthe baseband signals are not to be shrunk to a physical baseband that isnarrower than the specification, parameters that indicate that basebandsignals are not to be split into non-contiguous physical bands, andparameters that indicate additional guard-band sizes that are to beused.

The SVL forwards the registration request to the spectrum manager, block1104. If accepted, the spectrum manager allocates a portion of physicalspectrum and updates the map entries in the spectrum map, block 1106.The SVL may return a handle to the PHY that identifies the registeredvirtual baseband.

A wireless PHY submits a call to output virtual baseband signals to theSVL, block 1108. As part of the call, the wireless PHY provides anidentification of the virtual baseband, which prompts a look-up to thespectrum map for the physical spectrum. The wireless PHY provides sampleand length parameters that specify a pointer to the digital samples tobe output, and the number of digital samples to be output, respectively.

The wireless PHY submits a call to receive baseband signals, block 1110.During this call, the wireless PHY provides an identification of thevirtual baseband, a pointer to the sample buffer location, and thenumber of digital samples to be received. The SVL returns the samplesidentified by those parameters and passes them to the wireless PHY,block 1112.

Spectrum Map

As noted above, a spectrum map is employed to determine the mappingbetween the physical spectrum bands and the virtual spectrum bands. Foreach PHY, the table defines a virtual spectrum B^(V)(f,w) and theassociated (mapped) physical spectrum band B^(P)(f;w), where f is thecenter frequency and w is the bandwidth. A virtual spectrum band may beassociated with (mapped to) multiple bands B^(P) ₁(f₁,w₁), B^(P)₂(f₂,w₂) . . . B^(P) _(n)(f_(n),w_(n)) in embodiments where a virtualspectrum range is mapped to multiple physical spectrum ranges. A maptable of the spectrum map contains the processing information associatedwith the PHY layers. Non-limiting examples of processing informationincludes a reshaper identifier, a filter identifier (identifying asplitter), a radio identifier (identifying a radio, such as for examplein embodiments employing more than one radio in a device), and a timescale factor (for use in timing virtualization as discussed below). Thespectrum map may be established and maintained by a spectrum manager.Once a registration request has been accepted by the spectrum manager(as described elsewhere within this Detailed Description), the spectrummanager assigns a PHY identifier to the registered PHY and adds a newentry to the map table. As discussed elsewhere within this DetailedDescription, a spectrum virtualization layer enforces the map table.

Timing Virtualization

When an SVL maps a virtual baseband to a physical band with a narrowerwidth, it takes more time to transfer baseband signals than a PHYprotocol would expect. For example, if an 802.11a PHY with a 20 MHzvirtual baseband is mapped to a 10 MHZ physical baseband, it may takethe SVL 8 μs to send a symbol instead of the 4 μs as expected by thePHY. These changes in timing may impact the operation of the wirelessprotocols if the wireless protocols rely on absolute time information.For example, Network Allocation Vector (NAV) and ACK timeout wouldexpire pre-maturely if the transmitting time of PHY signal is extended.Embodiments therefore employ timing virtualization.

FIG. 12 is a flow diagram showing an example process 1100 for timingvirtualization. The process 1200 of FIG. 12 may, but may not, beimplemented in the communication module 128 in FIG. 1, communicationmodule 240 of FIG. 2, transmission 800 of FIG. 8, environment 700 ofFIG. 7, architecture 900 of FIG. 9, and/or SVL 1002 in FIG. 10. Someportions of the processes shown in FIG. 12 may be implemented bycomputer-executable instructions. Generally, computer-executableinstructions can include routines, programs, objects, components, datastructures, procedures, modules, functions, and the like that performparticular functions or that implement particular abstract data types.The processes can also be practiced in a distributed computingenvironment where functions are performed by remote processing devicesthat are linked through a communication network. In a distributedcomputing environment, computer-executable instructions may be locatedin local and/or remote computer storage media, including memory storagedevices.

The exemplary processes are illustrated as a collection of blocks in alogical flow graph representing a sequence of operations that can beimplemented in hardware, software, firmware, or a combination thereof.The order in which the processes are described is not intended to beconstrued as a limitation, and any number of the described processblocks can be combined in any order to implement the process, oralternate processes according to various embodiments of the presentdisclosure. Additionally, individual blocks may be omitted from theprocess without departing from the spirit and scope of the subjectmatter described herein. In the context of software, the blocksrepresent one or more computer instructions that, when executed by oneor more processors, perform the recited operations.

Referring back to FIG. 12, in process 1200, an SVL employing timingvirtualization presents a virtual clock to the wireless protocol (PHY),block 1202. The ticking rate of the virtual clock is adaptive accordingto the actual allocated physical spectrum bands. In one non-limitingexample, if b_(s) is the aggregated bandwidth of allocated physicalbands, and b_(v) is the width of virtual baseband, then the SVL adjuststhe ticking rate by a factor of b_(s)/b_(v).

During transmission, the PHY protocol modulates a data stream on avirtual baseband according to the virtual transmission frequency range,utilizing the virtual clock ticking rate, block 1204. The virtual clockticking rate can be thought of as slowing time down for the PHYprotocol, thereby allowing the PHY protocol to be used with the narrowerphysical baseband without modification of the PHY protocol. In otherembodiments, the virtual clock ticking rate may be faster than normal,in order to allow the virtual spectrum band to be mapped to a relativelylarger physical spectrum band in order to speed up transmissions withoutmodification of the PHY protocol.

During transmission, the SVL shapes the virtual baseband signal intophysical baseband signals according to the physical transmissionfrequency range, block 1206. The SVL passes the modulated physicalbaseband signals to the radio front-end for transmission on the physicaltransmission frequency ranges, block 1208.

During reception, the RF front-end receives RF signals on the physicaltransmission frequency ranges, block 1210. The RF front-end digitizesthe received analog signals and generates physical baseband signals tobe sent to the SVL, block 1212.

The SVL inverse shapes the received physical baseband signals intovirtual baseband signals, and sends them to the PHY protocol accordingto the virtual clock tick rate, block 1214. The PHY protocol demodulatesthe signal, and extracts the underlying digital data, block 1216.

Timing virtualization may require MAC and other high layer protocols tobe modified in order to get timing information only from the virtualclock. Many MAC implementations have common clock applicationprogramming interfaces (APIs) that refer to a single clock source.Therefore, embodiments re-implement these clock API functions. Forwireless protocols that have not been modified to support timingvirtualization, a policy can be set to ensure that its physicalfrequency band can be implemented in order to avoid the problemaltogether. Such a policy would cause the SVL to allocate enoughphysical bands to ensure that signal timing does not need to change.

RF Front-End Multiplexing

Spectrum virtualization according to various embodiments may support themultiplexing of multiple PHY onto a single wideband RF front-end. An SVLmay ensure that the width of the wideband RF front-end accommodates thewidth of physical bands allocated to the multiple PHY. The SVL includesmixers and splitters to support multiple PHY multiplexing.

A mixer may sit in the transmitting chain, and be configured to collectthe physical baseband signals of the multiple PHY (after reshaping),scale the signals' amplitudes according to individual ones of the PHYs'power masks, and then add (mix) the physical baseband signals togetherprior to sending them to a DAC in the RF front-end. A splitter containsa set of band-pass filters that match a physical band that has beenallocated to the multiple PHYs. For PHYs that have been mapped tononcontiguous physical bands, filters for all the noncontiguous bandsare combined by the mixer to form a single band-selective filter. Thesplitter applies a matched band-selective filter for each PHY, and thefiltered signal samples are fed to the corresponding reshaper that hasbeen mapped to the respective PHY.

If a base station or wireless client device has only one RF front-end,and that one RF front-end is half-duplex, multiplexing multiple PHY mayinclude careful scheduling, since a half-duplex RF front-end can onlytransmit or receive at any one time. Thus, the SVL may schedule thesignals for multiple PHYs to be transmitted simultaneously, and the SVLmay schedule the signals for multiple PHYs to be receivedsimultaneously. To accommodate these scheduling requirements, SVLsaccording to embodiments include buffers to temporarily hold basebandsamples when the RF front-end is receiving. The SVL defers thetransmissions until the receiving is done (i.e. upon detection of nosignal power on the receive chain of the RF front-end). The SVL can hidethe resulting buffering latency from the PHY layers by subtracting thelatency from the virtual time, such as by reducing a tick rate of avirtual clock.

A full-duplex mode can be achieved with a full-duplex RF front-end, orby attaching two half-duplex RF front-ends to the SVL. In embodiments,the sending and receiving bands may be orthogonal and one or more analognotch (band-stop) filters may be applied by the SVL to filter outself-transmitted signals in order to prevent the receiving chain frombeing saturated.

Computer-Readable Media

Depending on the configuration and type of computing device used, memory204 of white space base station 200 in FIG. 2, memory 304 of white spacefinder service 300 in FIG. 3, memory 708 of base station 702 in FIG. 7,and/or memories 718 and 726 of wireless clients 704 and 706 in FIG. 7may include volatile memory (such as random access memory (RAM)) and/ornon-volatile memory (such as read-only memory (ROM), flash memory,etc.). Memories 204, 304, 708, 718, and/or 726 may also includeadditional removable storage and/or non-removable storage including, butnot limited to, flash memory, magnetic storage, optical storage, and/ortape storage that may provide non-volatile storage of computer readableinstructions, data structures, program modules, and other data for whitespace base station 200, white space finder service 300, base station702, and/or wireless clients 704 and 706.

Memories 204, 304, 708, 718, and 726 are examples of computer-readablemedia. Computer-readable media includes at least two types ofcomputer-readable media, namely computer storage media andcommunications media.

Computer storage media includes volatile and non-volatile, removable andnon-removable media implemented in any process or technology for storageof information such as computer-readable instructions, data structures,program modules, or other data. Computer storage media includes, but isnot limited to, phase change memory (PRAM), static random-access memory(SRAM), dynamic random-access memory (DRAM), other types ofrandom-access memory (RAM), read-only memory (ROM), electricallyerasable programmable read-only memory (EEPROM), flash memory or othermemory technology, compact disk read-only memory (CD-ROM), digitalversatile disks (DVD) or other optical storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other non-transmission medium that can be used to storeinformation for access by a computing device.

In contrast, communication media may embody computer-readableinstructions, data structures, program modules, or other data in amodulated data signal, such as a carrier wave, or other transmissionmechanism. As defined herein, computer storage media does not includecommunication media.

CONCLUSION

Although the disclosure uses language specific to structural featuresand/or methodological acts, the invention is not limited to the specificfeatures or acts described. Rather, the specific features and acts aredisclosed as illustrative forms of implementing the invention.

What is claimed is:
 1. A base station, comprising: a radio transceiver;a spectrum virtualization module configured to exchange physicalbaseband signals with the radio transceiver, the spectrum virtualizationmodule further configured to perform baseband signal shaping to convertthe physical baseband signals into and from virtual baseband signalsgenerated according to one or more virtual frequency bands of a wirelesstransmission protocol of the spectrum virtualization module; and aspectrum manager including a decision module, the decision moduleconfigured to determine, based on one or more transmission policies, aspectrum allocation that maps one or more physical frequency bandsavailable in a geographic area of the base station to the one or morevirtual frequency bands in accordance with the wireless transmissionprotocol for baseband signal shaping by the spectrum virtualizationmodule.
 2. The base station of claim 1, further comprising: one or moreprocessors; memory; and a plurality of instructions stored on the memoryand which, upon execution by the one or more processors, cause the whitespace base station to implement one or both of the spectrum manager orthe spectrum virtualization module.
 3. The base station of claim 1,wherein the spectrum manager further includes an availability moduleconfigured to query a white space finder service for the one or morephysical frequency bands based at least in part on the geographic areaof the base station, and to receive data indicative of the one or morephysical spectrum bands.
 4. The base station of claim 3, wherein theavailability module is configured to receive a revocation from the whitespace finder service of some or all of the one or more physicalfrequency bands, and wherein the decision module is further configuredto modify the spectrum allocation based on the revocation.
 5. The basestation of claim 1, wherein the radio transceiver includes sensinghardware configured to determine the one or more physical frequencybands, and wherein the spectrum manager further includes an availabilitymodule configured to query the sensing hardware for the one or morephysical frequency bands.
 6. The base station of claim 1, wherein thespectrum manager further includes a policy module including the one ormore transmission policies.
 7. The base station of claim 1, wherein thetransmission policies include regulatory policies regarding the one ormore physical frequency bands including one or more of guard bandrequirements for the one or more physical frequency bands, time or timesthat the one or more physical frequency bands are available for wirelesstransmission, or transmission power levels of the one or more physicalfrequency bands.
 8. The base station of claim 1, wherein thetransmission policies include policies defined by the wirelesstransmission protocol including one or more of bandwidth requirements ofthe wireless transmission protocol, requirements for single ormulticarrier modulation, power transmission masks, guard-bandrequirements, duplex or simplex transmission requirements, or variableupload and download bandwidth requirements.
 9. The base station of claim1, wherein the spectrum allocation maps multiple ones of the one or morephysical frequency bands to a single virtual spectrum band of the one ormore virtual spectrum bands.
 10. The base station of claim 1, whereinthe spectrum allocation maps a single one of the one or more physicalspectrum bands to multiple ones of virtual spectrum bands.
 11. The basestation of claim 1, wherein the spectrum virtualization module isfurther configured to perform baseband signal shaping to convert otherphysical baseband signals into and from other virtual baseband signalsgenerated according to one or more other virtual frequency bands ofanother wireless transmission protocol of the spectrum virtualizationmodule, and the decision module is further configured to determine,based on one or more other transmission policies, another spectrumallocation that maps one or more other physical frequency bandsavailable in the geographic area to the one or more other virtualfrequency bands in accordance with the other wireless transmissionprotocol for baseband signal shaping by the spectrum virtualizationmodule.
 12. A system comprising: one or more processors; memory; and aplurality of programming instructions stored on the memory and which,upon execution by the one or more processors, cause the one or moreprocessors to implement a white space finder, the white space finderincluding: a propagation module configured to determine, based at leaston a location of a primary wireless device, a geographic area over whichwireless transmissions by the primary wireless device are likely topropagate; and an interference determination module configured todetermine, based at least on location information associated with asecondary wireless device, data indicative of one or more transmissionfrequency ranges on which the wireless transmissions of the secondarywireless device will not interfere with the primary wireless device. 13.The system of claim 12, wherein the white space finder further includesa reception module configured to receive, from the secondary wirelessdevice, the location information of the secondary wireless device and arequest for available physical frequency bands for wirelesstransmission.
 14. The system of claim 12, wherein the propagation moduleis further configured to determine the geographic area based on terraindata associated with the location of the primary wireless device. 15.The system of claim 12, wherein the white space finder further comprisesa revocation module, configured to transmit to the secondary wirelessdevice a revocation of the one or more transmission frequency ranges,the revocation of the one or more transmission frequency ranges basedon: reception of a message from a voluntary donor of the one or moretransmission frequency ranges revoking use of the one or moretransmission frequency ranges, or expiration of a time of availabilityof the one or more transmission frequency ranges.
 16. The system ofclaim 12, wherein the one or more transmission frequency ranges are in afrequency spectrum reserved for television broadcast channels and theprimary wireless device comprises a television signal transmitter.
 17. Amethod comprising: receiving, by a white space device, data indicatingone or more locally available, non-interfering physical transmissionfrequency ranges at a location of the white space device, the one ormore locally available, non-interfering physical transmission frequencyranges determined by a white space finder service; selecting, by thewhite space device, some or all of the one or more locally available,non-interfering physical transmission frequency ranges that match one ormore policies stored on the white space device; mapping, by the whitespace device, the some or all of the one or more locally available,non-interfering physical transmission frequency ranges to one or morevirtual transmission frequency ranges of the wireless transmissionprotocol; and transmitting, by the white space device, transmission bitsaccording to the wireless transmission protocol on the mapped one ormore physical transmission frequency ranges.
 18. The method of claim 17,further comprising querying the white space finder service for the dataindicating one or more locally available, non-interfering physicaltransmission frequency ranges at a location of the white space device,and wherein the one or more locally available, non-interfering physicaltransmission frequency ranges are determined at least on the location ofthe white space device and propagation modeling that utilizes at leastterrain data associated with a geographical area of a primary wirelessdevice.
 19. The method of claim 17, further comprising: receiving, bythe white space device from the white space finder service, a revocationof some of the one or more locally available, non-interfering physicaltransmission frequency ranges; and re-mapping, in response to therevocation, different ones of the one or more locally available,non-interfering physical transmission frequency ranges to the one ormore virtual transmission frequency ranges of the wireless transmissionprotocol.
 20. The method of claim 17, wherein the policies include guardband requirements, one or more of bandwidth requirements of the wirelesstransmission protocol, requirements for single or multicarriermodulation, power transmission ranges, duplex or simplex transmissionrequirements, or variable upload and download bandwidth requirements.